The present invention relates to containers in general, and more particularly to barrel-shaped containers of synthetic plastic material.
Barrel-shaped containers of synthetic plastic material are already known and they are finding ever-increasing use in various fields of human endeavour, such as for storing beverages and other liquids or flowable materials. Such containers are very inexpensive, particularly when produced by a blow-molding process, and they do not adversely affect the liquids contained therein. In addition thereto, such containers have a much smaller weight than conventional barrels for the same capacity, while being capable of withstanding internal and external forces to which the such barrels are subjected during storage, handling and use. However, experience with containers of this type has shown that they are still possessed of certain drawbacks which prevented such containers from even more extensive use.
Owing to the peculiar qualities of the blow-molding process, the conventional containers of this type have been formed with an annular projection of a generally U-shaped axial section, to which projection a radial outward flange of a lid of a container was connected by means of a ring-shaped element urging the flange towards the radial projection. The formation of such radial projection was heretofore necessary in order to assure that the material being blow-molded fully penetrates into a recess in the mold usd for the blow-molding process.
In one of the conventional containers of this type, the radial projection was formed between the body portion and the neck portion of the container, and represented a region of weakness in the container, having a particularly low resistance to axial forces transmitted from the neck portion to the body portion or vice versa. While this may not have been crucial for many uses of such conventional containers, it was a very serious drawback when a plurality of such containers had to be stacked on top of one another. Under these circumstances, the weight of the superimposed containers acted on the lower containers, and particularly on the lids thereof, from which it was transmitted to the neck portions of the lower containers and from there to the radial projections. These latter projections then acted as deformable folds so that, when the weight of the upper containers was radially offset from the central axis of the lower containers, the radial projection deformed more at some regions of the container than at others, thus presenting the danger that the entire stack of superimposed containers may have tilted over. In addition to endangering the personnel handling such containers, the tilting over of the stack and the subsequent impact of the upper containers upon the floor of the storage space brought about the danger of substantial damage to the impacted containers, and in particular disassociation of the lids from the remainders of the containers and thus spilling of the contents of such containers.
To remedy this situation it has already been proposed to form the radial projection with a plurality of indentations equidistantly spaced about the periphery of the radial projection, the presence of such indentations resulting in a substantial stiffening of the radial projections, whereby the adverse effects of the deformable fold have been almost entirely eliminated and the axially oriented forces were transmitted between the neck portion and the body portion directly and in a gradual and almost uniform manner.
An important disadvantage of this solution to the outstanding problem is that the indentations cannot be made arbitrarily deep in order to improve the axial stiffness of the radial projection. Another drawback of this solution is that the radial stiffness of the radial projection is reduced by the presence of such indentations. Therefore, it was necessary to stabilize the radial projection by addition of material in the radial direction.
Another important disadvantage of the containers which have been described above is that the conventional containers had annular recesses within the radial projections, in which recesses deposits from the fluids accommodated within such containers tended to form which it was difficult if not impossible to remove when cleaning the containers for further use.